diff --git a/src/main/java/com/github/davidmoten/rtree/OnSubscribeSearch.java b/src/main/java/com/github/davidmoten/rtree/OnSubscribeSearch.java
index 950e45d7..1f23865d 100644
--- a/src/main/java/com/github/davidmoten/rtree/OnSubscribeSearch.java
+++ b/src/main/java/com/github/davidmoten/rtree/OnSubscribeSearch.java
@@ -86,6 +86,7 @@ private void requestSome(long n) {
                     if (st.isEmpty()) {
                         if (!subscriber.isUnsubscribed()) {
                             subscriber.onCompleted();
+                            break;
                         } else
                             break;
                     } else if (requested.addAndGet(-r) == 0)
diff --git a/src/test/java/com/github/davidmoten/rtree/RTreeTest.java b/src/test/java/com/github/davidmoten/rtree/RTreeTest.java
index 78ee783e..438b8efa 100644
--- a/src/test/java/com/github/davidmoten/rtree/RTreeTest.java
+++ b/src/test/java/com/github/davidmoten/rtree/RTreeTest.java
@@ -41,8 +41,10 @@
 
 import rx.Observable;
 import rx.Subscriber;
+import rx.functions.Action1;
 import rx.functions.Func1;
 import rx.functions.Func2;
+import rx.observables.GroupedObservable;
 
 public class RTreeTest {
 
@@ -901,6 +903,82 @@ public void testIntersectsPointLine() {
         assertTrue(Intersects.lineIntersectsPoint.call(line(1, 1, 2, 2), point(1, 1)));
     }
 
+    @Test(timeout = 3000)
+    public void testGroupByIssue40() {
+        RTree<Integer, Geometry> tree = RTree.star().create();
+
+        tree = tree.add(1, Geometries.point(13.0, 52.0));
+        tree = tree.add(2, Geometries.point(13.0, 52.0));
+        tree = tree.add(3, Geometries.point(13.0, 52.0));
+        tree = tree.add(4, Geometries.point(13.0, 52.0));
+        tree = tree.add(5, Geometries.point(13.0, 52.0));
+        tree = tree.add(6, Geometries.point(13.0, 52.0));
+
+        Rectangle rectangle = Geometries.rectangle(12.9, 51.9, 13.1, 52.1);
+        assertEquals(Integer.valueOf(6), tree.search(rectangle).count().toBlocking().single());
+        assertEquals(Integer.valueOf(2), tree.search(rectangle).doOnRequest(new Action1<Long>() {
+            @Override
+            public void call(Long n) {
+                System.out.println(n);
+            }
+        }).groupBy(new Func1<Entry<Integer, Geometry>, Boolean>() {
+            @Override
+            public Boolean call(Entry<Integer, Geometry> entry) {
+                System.out.println(entry);
+                return entry.value() % 2 == 0;
+            }
+        }).flatMap(
+                new Func1<GroupedObservable<Boolean, Entry<Integer, Geometry>>, Observable<Integer>>() {
+                    @Override
+                    public Observable<Integer> call(
+                            GroupedObservable<Boolean, Entry<Integer, Geometry>> group) {
+                        return group.count();
+                    }
+                }).count().toBlocking().single());
+    }
+
+    @Test(timeout = 3000)
+    public void testBackpressureSearchWhenLotsRequestedButNotMaxValue() {
+        RTree<Integer, Geometry> tree = RTree.star().create();
+
+        tree = tree.add(1, Geometries.point(13.0, 52.0));
+        tree = tree.add(2, Geometries.point(13.0, 52.0));
+        tree = tree.add(3, Geometries.point(13.0, 52.0));
+        tree = tree.add(4, Geometries.point(13.0, 52.0));
+        tree = tree.add(5, Geometries.point(13.0, 52.0));
+        tree = tree.add(6, Geometries.point(13.0, 52.0));
+
+        Rectangle rectangle = Geometries.rectangle(12.9, 51.9, 13.1, 52.1);
+
+        tree.search(rectangle).doOnRequest(new Action1<Long>() {
+            @Override
+            public void call(Long n) {
+                System.out.println(n);
+            }
+        }).subscribe(new Subscriber<Object>() {
+
+            @Override
+            public void onStart() {
+                request(Long.MAX_VALUE - 100);
+            }
+
+            @Override
+            public void onCompleted() {
+            }
+
+            @Override
+            public void onError(Throwable arg0) {
+
+            }
+
+            @Override
+            public void onNext(Object arg0) {
+                request(1);
+                request(1);
+            }
+        });
+    }
+
     private static Func2<Point, Circle, Double> distanceCircleToPoint = new Func2<Point, Circle, Double>() {
         @Override
         public Double call(Point point, Circle circle) {
@@ -947,4 +1025,8 @@ private static Rectangle r(double n, double m) {
     static Rectangle random() {
         return r(Math.random() * 1000, Math.random() * 1000);
     }
+
+    public static void main(String[] args) {
+        System.out.println(Long.MAX_VALUE);
+    }
 }